[BB-2683] Add python 3.8 support (#83)

Add python 3.8 support

Author: shimulch

.travis.yml

@@ -4,6 +4,7 @@ dist: xenial
 python:
   - "2.7"
   - "3.5"
+  - "3.8"
 
 services:
   - xvfb

requirements-dev.txt

@@ -1,8 +1,14 @@
 # Internationalization and Localization requirements
--e git://github.com/edx/xblock-sdk.git@v0.1.6#egg=xblock-sdk==v0.1.6
-Django==1.11.25
+-e 'git://github.com/edx/xblock-sdk.git@v0.1.6#egg=xblock-sdk==v0.1.6 ; python_version == "2.7"'
+-e 'git://github.com/edx/xblock-sdk.git@0.2.2#egg=xblock-sdk==v0.2.2 ; python_version > "2.7"'
+
+Django~=1.11; python_version == '2.7'
+Django~=2.2; python_version > '2.7'
+
 # Latest version(1.0.4) of django-appconf do not support python 2
-django-appconf==1.0.3
+django-appconf==1.0.3; python_version == '2.7'
+django-appconf==1.0.4; python_version > '2.7'
+
 django-statici18n==1.8.2
 transifex-client==0.12.1
 edx-i18n-tools==0.5.0